Patent GB-711969-A (GB)
Title: Method and apparatus for moulding discs of polyethylene or other bodies of thermo-plastic material on to an electric conductor or other core
Inventor: DAVIES ROBERT WILLIAM
IPC: B29C70/74
Filed: 1951-07-11
Abstract: 711,969. Moulding discs of polythene &c. on electrical conductors &c. BRITISH INSULATED CALLENDER'S CABLES, Ltd. July 11, 1952 [July 11, 1951], No. 16461/51. Class 87 (2) A method of moulding a succession of discrete bodies of thermoplastic material on to a core comprises (a) advancing the core along a straight path through a mould cavity whilst reciprocating the mould cavity in the direction of said path; (b) injecting thermoplastic material into the mould cavity during each cycle of reciprocation; (c) allowing or causing the material to set whilst the cavity is travelling forward in the same direction as the core and at the same speed as the core; (b) opening the mould before the mould cavity reaches the end of its forward stroke to allow the moulded body to pass forward from the mould; (e) thereafter re-closing the mould, preferably during its return stroke. Injection may take place whilst the mould cavity is stationary or partly when it is stationary and partly when it is travelling forwardly with the core. After injection, the material in the mould cavity may be compressed by movement of the two end walls of the mould towards each other. The invention is described in connection with the moulding of discs of polyethylene or other thermoplastic material on a wire core intended to be the inner conductor of a concentric conductor cable. The apparatus shown (Fig. 1 elevation, Fig. 2 plan) comprises a fixed cooled block 1 having a horizontal bore 3 within which slides a hollow plunger 8. Through the plunger is fed, from right to left, a wire core 38. Thermoplastic material is injected through duct 39 into a mould.cavity 40 to form discs on the wire. core. The cavity 40 is formed by the space, in bore 3, between the left-hand end of plunger 8 and .the right-hand end of hub parts 23 projecting from a member formed in two or more parts 21, 22 slidably supported in a block 25. The block 25 and the hollow plunger 8 are secured to a framework comprising four rods 5 which slide in bores 4 in block 1, and this framework is reciprocated by means of cams 11 and links 17. The parts 21, 22 carry rollers 28 which co-act with a fixed cam 31. Operation :-From the position shown in Fig. 2, the mould cavity having been filled, the framework of rods 4 and the plunger 8 and block 25 carried thereby advance to the left at the same speed as the wire core 38, the mould cavity being thus cut off from the supply of thermoplastic material. As the framework advances the rollers 28 ride up cam 31, the hub parts 23 thus opening. The framework dwells in its advanced position and the wire core, with the recently-moulded disc thereon moves onwards to the left. The framework then retracts to the right, and during retraction the hub parts are forced together by springs 34. The framework dwells in the position shown and then again advances to the left, the sequence of operations being repeated. Thermoplastic material is fed into the mould during part of the retraction, during the dwell, and during part of the advance.